This invention relates generally to firefighting equipment and more particularly to a system for introducing chemical foamant into a fire fighting stream.
Systems for introducing chemical foamants and/or compressed air into a firefighting stream are known and are referred to in the art by the terms CAFS (compressed air foam systems) and WEPS (water expansion pumping systems). A typical system includes a foam injection system, a water pumping system, and an air compressor. When employing mixture ratios of 1 cfm of air to 1 gpm of water, these systems can produce very desirable results in firefighting by the use and application of "Class A or B" foams to help achieve fire suppression and to deal with increased fire loads and related hazards.
One system which includes a foam injection system, a water pumping system, and an air compressor is disclosed in co-owned U.S. Pat. No. 5,145,014. The system includes an air compressor for injecting air into the fire stream and includes a foam injection system in the form of a foam proportioner which injects chemical foamant into the fire stream. The foam proportioner is powered by drawing water off of the fire stream, which reduces the pressure head of the fire stream. In addition, the foam proportioner does not include any mechanism for specifically selecting and controlling the proportion of chemical foamant that is introduced into the water stream flowing through the fire hose. For a more detailed description of such a foam proportioner, reference may be had to co-owned U.S. Pat. No. 4,633,895.
Other systems for introducing a chemical foamant into a water stream are disclosed in U.S. Pat. Nos. 5,232,052 and 5,494,112. In such constructions, the foam pumps are lowered by electric and/or hydraulic motors. However, the electric motors and hydraulic motors require a power source which must be mounted on the fire fighting apparatus, such as a fire truck. The addition of such a power source to the fire fighting apparatus is expensive, space consuming, and adds weight to the fire fighting apparatus.
Accordingly, it is believed that it would be an improvement in this art to provide a foam injection system which does not require an additional power source and which permits selective and accurate control of the proportion of chemical foamant introduced into the fire stream.